1. Field of the Invention
This invention relates to a processing apparatus designed to subject moving-picture information to highly efficient encoding or decoding.
2. Description of the Prior Art
Japanese published unexamined patent applications 6-231235 and 7-296170 disclose prior-art compressing apparatuses in which information of equal-luminance lines (iso-luminance lines) is generated from picture luminance information, and feature points are derived from the equal-luminance lines. Then, the picture luminance information is compressed in response to information of the feature points.
A portion of a picture which has an abrupt change of luminance is referred to as a picture edge portion. On the other hand, a portion of a picture which has a gradual change of luminance is referred to as a picture gradation portion.
In a prior-art expanding apparatus for compression-resultant picture luminance information, it is difficult to discriminate a picture edge portion and a picture gradation portion from each other. The same interpolation using mean values is applied to both the recovery of original information of the picture edge portion and the recovery of original information of the picture gradation portion. As a result, the recovered picture edge portion tends to have a less abrupt change of luminance. On the other hand, the recovered picture gradation portion tends to have a step-like difference in luminance.